1. Technical Field
The present invention relates to a liquid ejecting apparatus such as an ink jet type printer, for example, and a cleaning method in a liquid ejecting apparatus.
2. Related Art
Heretofore, as a liquid ejecting apparatus which ejects liquid onto a target, an ink jet type printer has become widely known. The printer is made so as to carry out printing (image formation) on the target by ejecting ink (liquid), which is supplied to a recording head (a liquid ejecting head), from nozzles formed in the recording head.
In such a printer, if the mixing-in of air bubbles, the rising of a meniscus, the thickening of ink, or the like occurs, satisfactory ejection of ink cannot be attained, thereby causing the lowering of printing quality. For this reason, in such a printer, for example, as described in JP-A-2007-152725, cleaning (pressurization cleaning) is performed by pressuring and supplying ink from the upstream side which is an ink cartridge side containing ink to the downstream side which is the recording head side, thereby discharging ink from the nozzle.
In such a printer, back pressure is applied to ink, thereby making a meniscus of ink be located in the vicinity of a nozzle orifice. As a configuration of applying back pressure to ink, in general, a one-way valve is used which allows passage of ink from the upstream side to the downstream side in a case where the downstream side has been decompressed. The one-way valve has a pressure chamber, in which a volume changes in accordance with a change in pressure on the downstream side, and if the downstream side is decompressed, the pressure chamber contracts, thereby opening the valve, whereas a valve closed state is maintained even if ink is pressurized and supplied from the upstream side.
For this reason, like the printer of JP-A-2007-152725, in the case of pressurizing and supplying ink from the cartridge side, thereby supplying it to the nozzle side, ink remains pressurized further in the downstream side than the one-way valve.
Further, in such a printer, ink mist which is generated accompanying the ejection of ink, or ink overflowed from the nozzle adheres to a nozzle formation face of the recording head, in which the nozzles are formed, whereby the nozzle formation face is contaminated. Accordingly, for example, as described in JP-A-2009-178867, wiping which sweeps the nozzle formation face by using a wiper is performed, thereby removing foreign materials adhered to the nozzle formation face.
Incidentally, ink supplied to the recording head forms a meniscus in the vicinity of the nozzle orifice and is ejected from the nozzle in accordance with the driving of a piezoelectric element. For this reason, if the wiper comes into contact with the nozzle formation face, there is a possibility that ink may flow out down the wiper. Accordingly, in the printer of JP-A-2009-178867, the contact between the wiper and ink is suppressed by performing wiping in a state where the meniscus is drawn into the nozzle by driving the piezoelectric element.
Incidentally, in a case where ink is pressurized further at the downstream side than the one-way valve, since a pressurizing force is also transmitted to the one-way valve, the pressure chamber expands, thereby accumulating the pressurizing force. For this reason, like the printer of JP-A-2007-152725, in a case where cleaning is performed by pressurizing ink further at the downstream side than the one-way valve, the back pressure of ink cannot be adjusted by the one-way valve, and further, the pressurizing force accumulated in the pressure chamber is transmitted to the nozzle side. Even after the end of cleaning, there is a fear that ink overflows from the nozzle, such that a lot of ink is wasted with the cleaning.
Further, in the printer described in JP-A-2009-178867, the meniscus of ink is made to be located in the vicinity of the nozzle orifice by a capillary force. Since ink is forced to the nozzle orifice side by the capillary force of the nozzle, in the case of raising the meniscus by driving the piezoelectric element, it is difficult to maintain the risen position.
Accordingly, as the manner of providing a suction force larger than the capillary force of the nozzle, the manner of suctioning ink by using a pump can be considered. However, in the case of providing a pump at a single flow path (liquid supply flow path) which communicates with a plurality of nozzles and suctions ink, thereby raising the meniscus, the more the distance from the pump to the nozzle is distant, the more difficult it is for the suction force of the pump to reach the nozzle. For this reason, the more the distance from the pump to the nozzle is distant, the more easily the position of the meniscus is lowered, so that variation occurs in position of the meniscus for each nozzle.
Therefore, if ink is supplied to the nozzle side after the end of wiping, in the nozzle in which the meniscus is maintained at the risen position, the meniscus moves to the vicinity of the nozzle orifice. On the other hand, in the nozzle in which the meniscus has descended, there is a possibility that ink may overflow from the nozzle.